Radio receiving system



March 18, 1930. T. GONG-ORA; J'R

RADIO RECEIVING SYSTEM Filed Feb. 10, 1927 gnwntoz: '2'. 7710/7705Gonyo/q kr fluomu Patented Mar. 18, 1930 UNITED STATES P THQIVIASGONGORA, JR., OF ST LOUIS, MISSOURI RADIO RECEIVING SYSTEM Applicationfiled February 10, 1927. Serial No. 167,212.

This invention relates to radio-receiving systems, and theobject'thereof is toprovide a' system of that character that willpossess the combined advantages of great sensitivity, selectivity,volume, ease of control, tone quality, simplicity, and reduction orsuppression of static or strays, and the like, Systems have hithertobeen provided that are highly sensitive, but they have been extremelydiflicult to control. One such system that may be mentioned for thepurpose of illustration is the homodyne system of reception, in whichthe results are obtained by impressing the incoming carrier waves on thegrid circuit of a thermionic valve or tri-electrode vacuum tube normallyin a state of oscilla tion, the system being adjusted so that the localoscillations suppress the carrier Wave by the principle of zero-beatreception, as

will be understood by those skilled in the art. It is, however,extremely difficult to control and to adjust the local oscillations tothe proper frequency and phase relation to. the incoming waves, therebeing a tendency to instability and distortion of signals and theproduction of squeals, beat notes, and the like.

Briefly described, the present invention purposes broadly to impress theincoming waves on the plate or output circuit of a normally oscillatingreceiving system, instead of on the grid or controlling'circuit, so thatthe aforementioned condition of instability r is obviated. The presentinvention is applicable to homod'yne, heterodyne, and other circuits,and is not limited in its use to the two circuits which have beenselected for the purpose only of illustrating the invention.

In the accompanying drawing forming part of this specification, in whichlike numbers of reference denote like parts wherever they occur, theFigures 1 and 2 are diagrams which illustrate two embodiments ofthisinvention.

The oscillating circuits of Figures 1 and 2 comprise a plate 1, grid 2,and filament 3 of a thermionic valve or vacuum tube normally in a stateof oscillation, the grid circuit 4 including the usual grid condenser 5,grid resistance 6, tuning condenser '7, and

feed back or coupling coil 8, andthe plate circuit 9, including thecoupling coil 10, source of plate current supply or B battery 11,radio-frequency choke coil 12, andtele-' phone receiver 13. The filament3 is supplied with current from any suitable source, such as an Abattery '14, and thefilament current may be regulated by the 'rheostatin the filament circuit 16.

In Figure 1, a wave-collecting circuit 17,

including aerial 18, ground 19,'and adjust able inductance 20, isconnected to the plate circuit 9 through a lead 21. In Figure 2, thewave-collecting circuit 22 comprises antenna 18, ground 19, adjustableinductances 6 23 and 24, and coupling coils 25 and 26, coil 25 beingincluded in the plate circuit ,9 and coil 26 in the'aerial circuit 22.Coils 25 and 26 and circuits 9 and 22 are connected by a lead 27 Acondenser 28 in Figure 2 prevents shorting of the battery 11.

The incoming modulated carrier waves are collected by the circuits 17and 22'and pass into the plate circuit 9, being prevented from passinginto the grid circuit 4 by the radiofrequency-choke coil 12. Theseparation of the -coils Sand 10 governs thecoupling of the grid andplate circuits 4: and 9, respectively, and by adjustingthe coupling tothe best point'the selectivity isincrea'sed or decreased, as desired. Itcan, also, be fixed at an optimum value. The frequencyof the circuit iis adjusted by the variablecondenser-Y to the. frequency of the incomingwaves, and the phase relation between the incoming waves and theoscillations of theplate circuit 9 is determined by adjusting theinductanceof aerial 17, and in the case of aerial 22, by adjusting thevariable inductances 23 and 24 and theco'upling coils and 26. The ad- 7justments of these coils and inductances, also assist in tuning theaerials, as will be un derstood by those skilled in the art.

"As is well known in the radio science, the

incoming modulated carrier wave that is 001- lected by the aerial iscomposed of a frequency 7 which is called the carrier wave, andmodulation frequencies f f 7, etc. In order to'simplify matters, let .itbe considered that these modulation frequencies, vwhich, are

' mitting station upon the carrier wave.

, whose value may be expressed by the algebraic sum of f and FM, or bythe quantity fi-FM.

wave is impressed upon the plate circuit 9 in such a way that the radiofrequency cur-- rent in the circuit 9 is of the same frequency as and inopposite phase, or at a phase angle of 1'80,.to the modulated radiofrequency striking the'aerial andground system, a condition of zero beatis obtained and the carrier wave is destroyed, leaving only in the platecircuit of thetube the modulating current FM, which was impressed at thetr a pls- 1s audio-frequency current FM is heard inthe phones 13. V a

The choke coil 12 is used in order to prevent theradio-frequency-carrier wave 7 from getting into the gridcircuit 4:through the filament connection. If this frequency were admitted intothe gridcircuit, it would produce low frequency beats which would makereception very difficult not impossible.

,A very large resistance'29, about twenty megohms, the magnitude ofwhich is determined by the constants of the tube and within certainlimits, also, by the frequency of the oscillating current in the tubecircuit, is used to provide a leakage path between the plate and thegrid, so as to highly resist the passage of the carrier waves and tomake the oscillation more stable. It, also, serves to impress theaudio-frequency currents, released in theplate circuit 9, upon the grid2, so that audio amplification is obtained thereby. v r

As is well known in the art, this system of reception is called thezero-beat, or homodyne, system of reception and is used forillu'strative purposes only, and not in a limiting sense. -Any othersuitable oscillating circuit may beused, such, for instance, as the.heterodyne for telegraphic purposes, when the beat current obtained maybe of any value other than zero, While theillustrated embodiments employan antenna and ground connection, other wave-collecting means may beemployed and coupled to the plate or out put circuit of an oscillatingsystem, such, for instance, as a loop, or a collector connected to theground alone, or to the antenna alone, -or an aerial and counterpoisecollector. Also,

the-collector need not be directly coupled or directly connected to theoutput circuit 9, butthe connection or coupling may beindirect' throughthe intermediacy of amplifiers or other devices or circuits. Thisinvention Now, if this modulated carrier;

can, also, be incorporated in a wave meter, transmitting system, orother devices.

The sensitivity and selectivity of this system is believed to be verymuch greater than that of any other system known at present. The volumeis the same as that obtained from a regenerative circuit at bestadjustment The tone quality is natural, provided it has notbeen'sacrificed for the sake of selectivity, when adjusting theoscillating circuit. The-signal isclear from all distortion, squeals,beat notes, and the like, and always athighest volumenfor each wavelength tuned. It is easy to tune without many adjustments, and canbe'designed so that it may be operated from a single dial. Since theaerial and ground is connected to the plate circuit and not to the gridcircuit, the static, strays, and the like are not amplified as in othercircuits or are not received at all, since the circuitis responsivepreferentially to a modulated carrier' wave, which is'reacted upon bythe local oscillator. A connection to'the ground can bev used only andno difference in" signal strength has been detected, provided the groundsystem is of the right inductance and capacity. When using an aerial anda ground or a ground connection only, the inductance or capacity or bothare varied forthe best operating point and there is no need of retuningfor each wave length thatis received, provided the range is within therange of frequencies produced by the local oscillator. 7

Having thus fully described this. invention, I hereby reserve thebenefit of all changes inform, arrangement, order, or use of parts, asit is evident that many minor changes may be madetherein withoutdeparting fromthe spirit of this invention or the scope of the followingclaims.

1 claim 1. A radio-receiving system for reproducing the modulating sidebands of a modulated carrier wave that comprisesa space discharge deviceand input and output circuits therefor having a common cathode, meansfortuning the system to the frequency of the incoming wave,wave-collecting. means coupled to the output circuit, and a filteroffering high impedance to the frequency of thecarrier wave but resonantto the modulating frequencies of the carrier wave, said filter beinglocated in the output circuit connection to the common cathode toexclude the carrier wave from the input circuit. 7 I

. 2. Means for reproducing the modulating side bands of a modulatedcarrier wave comprising a space discharge device and input and outputcircuits having a common cathode and coupled so as to produceoscillations therein, means for tuning the system to generate afrequencyequal to that of the carrier wave, means for superimposing themodulated carrier wave upon the outputcircuit,

signal means in the output circuit, the portion of said output circuitbetween the signal means and the common cathode having an impedance thatrepresses the carrier Wave but not its modulating frequencies.

3. Means for reproducing the modulating side bands of a modulatedcarrier Wave, comprising a space discharge device having a grid circuitand an anode circuit connected through a common cathode, both circuitsbeing coupled so as to produce oscillations, means for tuning the systemto generate a frequency equal to that of the carrier Wave, means forsuperimposing the modulated carrier Wave upon the anode circuit, asignal-indicating device in the anode circuit, and a filter located inthe anode circuit between the signal-indicating device and the commoncathode and offering high impedance to the frequency of the carrier Wavebut resonant to the modulating frequencies of the carrier Wave.

4. A receiving system for reproducing the modulating frequencies of amodulated carrier Wave, consisting of a space discharge device having acontrolling circuit and an anode circuit connected through a commoncathode, both circuits being inductively coupled so as to normallygenerate oscillations, means for tuning the system to generate afrequency equal to that of the modulated carrier Wave, signal collectingmeans included in the anode circuit, and a filter in series in the anodecircuit to exclude the modulated carrier Wave from entering thecontrolling circuit, by Way of the connections to the common cathode,but offering low impedance to the modulating frequencies of the carrierWave.

In testimony whereof I hereunto afiix my signature.

THOMAS GONGORA, JR.

